We propose an analysis of differential urban mortality using Philadelphia as a case study. Our theoretical concern is with the determinants of the sharp mortality decline that occurred in American cities at the end of the last century. We wish to isolate the contributions to the overall decline of currently competing explanations--improvements in medical care, sanitation and diet--whose separate affects have never been identified. Our research will be conducted in two-stages: the first, focusing on the period just prior to the mortality transition, will determine feasability and develop hypotheses in cross-sectional analysis (we expect the mortality decline to be observable among those in the population enjoying higher levels of living); the second stage, focusing on the period immediately following the transition, will test these hypotheses with new data from the death registers and the federal population manuscript census for 1900. We request funds now for only the first-stage study. Our findings should have policy implications where choices among competing resource allocation strategies to reduce mortality are involved. Using the Philadelphia register of individual deaths for full year following the federal population census of 1880, our research will examine four sub-projects: (1) the enumeration accuracy of the U.S. Population Census; (2) the differential in mortality by ethnic, racial and occupational groups as well as the general age, sex and cause-of-death patterns, with special emphasis on the mortality experience of Black-Americans; (3) the relationships between the household living arrangements that preceded death and the rates and patterns of mortality; and (4) the ecological correlates of spatially differentiated mortality, including topography, water and sewage facilities, housing characteristics, population densities and industrial pollutants. The proposed research will be conducted within the context of the Philadelphia Social History project, an interdisciplinary research effort supported since 1969 by agencies within NIMH, NSF and NEH. As such, the research will benefit considerably from the availability of an unusually large and detailed machine-readable data base that describes the urban environment and its diverse population groups and the involvement of pre- and post-doctoral scholars drawn from economics, demography, geography, (Text Truncated - Exceeds Capacity)